AF came!

Saturday morning my fiance and I tried to BD but little to my surprise 3 days late AF showed up. It's very different from any other period of mine before, it was light and short. Bright red blood but hardly filling a tampon. I came off BC back in Febraury and in march and April from what I can remember my periods were longer and heavier than this. I can't be pregnant can I? A periods a period right?